Figure 1

Proposed interactions between peptides (rectangles) and lipid bilayers. The gray and black represent hydrophilic regions. (a) Peptides are soluble in water but have a high affinity for binding to lipid bilayers. (b) Peptides inserting into the headgroup region stretch the membrane area, cause thinning of the chain region, and thus create an internal membrane tension. (c) Peptides preferentially bind to the edges of the pores, which has the consequence of loosening the internal membrane tension. (The depicted pores are called toroidal, or wormhole models [18]. Some peptides make barrel-stave pores [20]. The mechanism should be the same for both types of pores.)Reuse & Permissions

Figure 2

Membrane thickness measured as a function of the peptide concentration $P/L$. Lipid vesicles with bound peptides were collapsed into parallel multilamella, from which x-ray diffraction measured the phosphate-to-phosphate distance (PtP) of the bilayer [10, 16]. The hydrocarbon thickness $h$ was obtained by subtracting twice the phosphate to chain distance ($\sim 1\mathrm{nm}$) from PtP. Data of four different peptide/lipid systems are shown (from top): alamethicin in diphytanoyl phosphatidylcholine (DPhPC), alamethicin in a dioleoyl phosphatidylcholine (DOPC) and dioleoyl phosphatidylethanolamine mixture, melittin in DPhPC, and melittin in DOPC. (The data of alam/DPhPC and melittin/DOPC were reproduced from Ref. 10.) The arrows indicate the values for $P/L^{*}$ as measured by oriented circular dichroism [10].Reuse & Permissions